The invention relates generally to valve actuation systems which may be utilized as either apparatus for or method of actuating a valve. More particularly, the invention is intended to provide an improved system for actuating axially-rotated valves by providing actuation of the valve with single or multiple actuation features.
Rotary actuators have been used to control the positions of certain types of valves, rotary switches and other axially rotated mechanisms. The most prominent types of electrical rotary actuators may consist of rotary solenoids, stepper motors, synchronous motors and commutator motors. Selection among these is guided by the required range of rotary displacement, size limitations, maximum torque, cost and energy constraints. Electrically operated actuators may rely on one or more pairs of stator poles that generate an electromagnetic field, usually including either a ferromagnetic or permanent magnet rotor that responds to this field. Rotary solenoids generally operate through a small range of rotary displacement, due to a potentially rapid loss of magnetic field strength or limits on related axial motion. An operating range of 45xc2x0 may be increased to over 90xc2x0 by incorporating multiple stator poles, as illustrated by the Ledex BTR(copyright) rotary solenoid design. Another potential method of extending rotary displacement is to selectively excite multiple stator poles to create the effect of a rotating magnetic field, exemplified in U.S. Pat. No. 5,786,649. A closely related method of extending rotary displacement may include attaching either synchronous or stepper motors to the rotated shaft, as described in U.S. Pat. No. 4,672,247. An additional and commonly employed method may incorporate a direct-current (DC) excitation current with brushes and commutator to maintain magnetic field strength independent of rotational position.
These existing rotary actuators may pose several design limitations relative to operating an axially rotated valve such as the VOST(trademark) valve, as described in U.S. patent application Ser. Nos. 08/925,535 and 09/121,650, now U.S. Pat. No. 6,026,845, and in international application No. PCT/US98/18333, all hereby incorporated by reference. Conventional rotary solenoids may not provide the required 180xc2x0 of rotation. Synchronous and stepper motors may not provide sufficient torque-to-size ratio to be practical in the VOST(trademark) application, due to potentially smaller magnetic flux areas than solenoids of similar size. Synchronous and stepper motors, and including direct-current motors, may generally add unwanted cost, piece count and complexity.
Another potential limitation of existing rotary solenoids is the inability to latch in both the open and closed positions without a holding current. Many rotary actuators designed for binary valve positions have a quiescent and an energized state. Electric current is generally required to maintain the actuator in its energized state. For example, current must be supplied to a normally closed, rotary solenoid valve to hold it in the open position. Incorporating an actuator requiring an energized state for actuation increases the cost of energy and the challenge of heat removal in certain applications. Latching valves do exist that address this problem by exploiting the fluid pressure to hold the valve in position, exemplified in U.S. Pat. No. 4,672,247. This approach, however, requires a more complex fluid flow path, adding mass and cost to the valve.
The actuation system of the present invention addresses the inadequacies that may have existed with prior valve actuator systems. Accordingly, the present invention provides a valve actuation device and method for actuating axially-rotated valves. The present invention may even be considered in some aspects as a development away from that which was previously known in the art of valve actuation.
One embodiment of the invention may provide valve actuation comprising an actuation providing a first movement direction and wherein an actuating element is positioned outside of the flow path of the valve and actuates the valve without interfering with the flow of the valve. Actuation, therefore, may occur without interference to valve flow.
An embodiment of the invention may additionally provide a second actuation having a second movement direction non-congruent, and in preferred embodiments orthogonal, to a first movement of a first actuation.
An additional embodiment of the invention may further provide for guiding the valve during actuation. In preferred embodiments the guiding may be provided by guide elements, preferably bearings and bearing guides, to orient and provide rotational force or torque to the valve.
In particular and preferred embodiments, the actuation system may be provided through axially and radially oriented electromagnetic fields combined with mechanical conversion of axial to rotational motion. A rotary actuator may be provided that is attached to and operates the valve by means of a briefly applied direct current. The actuator may contain a main electrical winding and an armature, preferably shaft mounted, that together may produce axial thrust, and auxiliary electrical windings that exert a biasing torque or force on a preferably shaft-mounted, permanent magnet or armature. From either opened or closed position, this combination of thrust and torque may rotate the valve, and in a preferred embodiment in a helical motion, to the opposite valve position, and may allow for valve seal contact to be restored when actuated, and in preferred embodiments excitation current, is curtailed. In preferred embodiments, a combination of roller bearing guides and biasing torque may ensure full rotary motion as well as latching in the open or closed position of the valve.
It is an object, therefore, of the present invention to provide a novel system for actuating axially-rotated valves.
In particular, it is an object of the present invention to provide sufficient rotary displacement for valve actuators. A goal of the present invention therefore is to provide an axially-rotated valve actuation system that overcomes limited rotary displacement that may have resulted from previous rotary actuator systems. In particular, it is a goal of the present invention to provide axially rotated actuation of the VOST(trademark) valve through 180xc2x0 of angular displacement.
Furthermore, it is an object of the present invention to provide sufficient torque to effect proper valve actuation for axially-rotated valves. A goal of the present invention, therefore, is to provide adequate torque, for example in high-pressure valve applications, to alternate valve positions, and preferably within a minimum amount of time. It is an additional goal of the present invention to provide adequate torque to operate particular axially-rotated valves such as the VOST(trademark) valve.
A further object of the present invention is to provide an actuator for axially-rotated valves that allows the valve to remain in an open or closed position. A goal of the present invention, therefore, is to provide a valve actuation system that provides a fail-safe or fail-in-place feature that maintains the valve in an open or closed position and further allowing for the actuation system to be deactivated when the valve is opened or closed.
A further object of the present invention is to provide a hermetic seal between the fluid and environment in a valve actuation system. A goal of the invention, therefore, is to eliminate the need for valve stems and associated packing glands or seals. A further goal of the invention is to provide an actuation system that provides for actuation of a axially-rotated valve without interfering with flow through the valve.
It is a further object of the present invention to minimize internal valve seal wear that may occur over prolonged periods of valve actuation. A goal of the invention, therefore, is to provide an amount of reciprocating axial displacement during actuation to minimize seal wear. It is an additional goal of the present invention to provide adequate axial displacement during actuation of the VOST(trademark) valve""s rotating and stationary tubes to minimize seal wear.
It is further an object of the present invention to eliminate a possible need for manual actuation of a valve. A goal of the invention, therefore, is to provide a valve actuation system that may operate in a remote and unattended fashion by providing actuation and responsive armature features that allow for non-manual valve actuation.
Other objects of the invention are disclosed throughout other areas of the specification and claims. In addition, the goals and objectives may apply either in dependent or independent fashion to a variety of other goals and objectives in a variety of embodiments.